Traditionally, Japanese swords like katana and wakizashi are made from a grade of steel known as tamahagane. This steel is widely regarded for its ability to withstand abuse, to take and maintain a fine edge, and to withstand the rigors of differential tempering.
However, in the modern era, swordsmiths have a much larger pool of resources to draw from, and this includes advanced metal alloys, some of them in the 10XX series, which possess just the right balance of carbon to levy hardness and flexibility.
Some modern replicas, especially battle ready versions, are spring steel katana, often made from an alloy such as, or similar to, 5160.
What Is Spring Steel?
Spring steel constitutes a class of steel that is half designated by steel chemistry and the other half by heat treatment.
First, let’s talk about the alloy itself. Interestingly, spring steels tend to be higher in chromium than their “high carbon” counterparts. Generally excess chromium is eschewed as it can make steel too soft, but at the same time, too much carbon makes a steel brittle.
This is decidedly negative when it comes to swordsmithing, as an alloy that is too brittle will result in a blade that chips or breaks. Spring steels, which are not just softer, but which are heat treated to be more flexible, are better able to tolerate these abuses.
Some spring steels also contain a bit more silicon, which is also usually an undesirable additive in a steel alloy, but which will improve flexibility when the sword is properly tempered.
This brings up the heat treatment and tempering aspect of swordsmithing, which is one of the most important aspects of making a sword that’s suitable for live use.
The process can vary depending on the smith, but as a general rule, first the blade is annealed, then heat-treated to achieve high hardness, and then finally tempered to give it a high degree of flexibility.
This is done by heating the blade to a set temperature (dependent on the smith’s preferences) and then holding the blade at that temperature for an hour or more, typically up to two hours, before allowing the blade to slowly come down from that temperature.
This is sort of like “pseudo-annealing” but at a much lower temperature, and the temperature is held for a longer time before the blade is allowed to cool.
What this results in is a sword that is still reasonably hard and therefore able to take and hold an edge, but one that has a flexible, springy blade that can be bent without taking a set, or without breaking.
Elasticity, Ability to Absorb Repeated Blows Without Bending or Breaking
While Japanese swords have not traditionally been made from spring steel alloys, modern spring steel katana swords are highly sought after because of the performance they deliver.
Spring steel alloys are not just hard and tough, they are highly flexible and can often be bent by several degrees without taking a set, and without chipping, snapping or shattering.
This specifically makes them uniquely able to tolerate the abuses associated with live swordplay and cutting practice.
Repeatedly striking the sword against a target or obstacle increases the likelihood of chipping or otherwise damaging it, but with a spring steel blade, it’s less likely to occur, and the blade will likely last longer even when presented with hard use.
Here for a Spring Steel Katana?
If you’re interested in a spring steel katana, first look at True Swords. They carry a wide range of battle-ready swords, including Japanese swords such as katana, wakizashi, and odachi swords. Take a look through what they offer and get in touch with them directly if you have any questions.
